by Autumn Coleman
We all know that viruses infect people. We’ve seen them infect pets, other animals, and maybe even plants. But what about fungi? And no, they’re actually not considered plants; but you’ve probably seen sick plants too. So what would a sick fungus even look like?
Well, let’s see.
Figure 1: Shown here is the wheat blight fungus called Fusarium graminearum. On the left is a cultured virus-free fungi, and on the right, the fungus is infected. This virus is known as Fusarium graminearum mycotymovirus 1 (or FgMTV1/SX64 for short) and causes little to no effects on its host fungus.
There doesn’t seem to be much of a difference, right? And that’s because fungal viruses, known as mycoviruses, actually may not cause disease – at least not how we know it in fungi. There are many different types of fungi, and you’ve probably seen many varieties growing outside.
Similarly there are many fungal viruses present in each genera of fungi. According to multiple studies, many of these mycoviruses seemingly cause little to no noticeable effects in their fungal hosts. However, for others, these viruses can cause crippling effects, such as:
- Inhibiting fungi reproduction,
- Preventing the spread of fungi,
- Messing with fungi’s ability to eat,
- Altering their pigmentation.
Yet, for other fungi, viruses aid in their survival by providing beneficial effects, such as cold-resistance
In some other amazing cases, viruses actually help humans by preventing fungi from parasitizing other plants, animals, and even humans, through what is known as hypovirulence. And the inverse is true too! Mycoviruses can also cause hypervirulence – where fungi become better at infecting and degrading their hosts which may be plants, insects, or even people.
Figure 2: The above leaves have a fungal infection as shown by the lesion. The cryptic, hypovirulence, and hypervirulence leaves show the response of the fungi to a viral infection. Figure source (edited by author).
Now, what about immunity? Our body fights infections all the time, so do the fungi fight viruses if most of these mycoviruses cause little to no effects? The answer is yes! Fungi have an innate immune system that uses different types of machinery in its own DNA to prevent itself and other fungi from being infected.
Fungi have multiple amazing ways to protect themselves from viruses. One way is by silencing the virus genes, basically turning them off. They can also encapsulate and shoot out the genetic material of viruses. Plus, the fungal immune system can in some cases help them recognize other fungi and foreign genes trying to invade their space. This immune system stops different fungi from interacting, preventing diseases from spreading. This is really helpful for fungi because it means the disease usually can’t infect other fungi that aren’t the same kind.
So, this is cool and all, but what does this have to do with anything? Well, have you ever had mold grow on your fruit or vegetables before you could eat it? That’s a fungus. But imagine if we could treat that mold, and prevent food from spoiling so fast. How about more locally, those knot-like bulges on trees? What you’re seeing is actually a parasitic fungus infection called Black Knot.
Figure 3: Black Knot fungus infection, shown growing on a tree.
These knots of fungi eventually weaken and break down trees, however, imagine if we could prevent this. Mycoviruses are one method we could use, specifically through the effect of hypovirulence.
Figure 4: A brief example of crop or plant biocontrol methods potentially available in the future based on our current knowledge of mycoviruses.
We don’t know a huge amount about fungal viruses yet. It’s a new field of research founded only 30 years ago! But wouldn’t it be interesting if we could use this knowledge to help both the environment around us and ourselves? What else can you think of that we can use this for? If you want to find out more, why not check out the research yourself!
